Japan claimed their second straight win in the Pacific Nations Cup on Saturday, beating Tonga 41-7 at Hanazono Rugby Stadium to set up a winner-takes-all clash against the United States.

Japan, playing the second of four matches held in the lead-up to the Rugby World Cup, followed up their 34-21 win over Fiji by dominating the 'Ikale Tahi, ranked 14th in the world, on an impressive effort from their pack.

The Brave Blossoms were led by assistant coach Tony Brown after head coach Jamie Joseph returned to New Zealand following the death of his mother. World No. 11 Japan have now won nine of their 18 meetings against Tonga.

"I thought it was a very tough test match. When we had the opportunity to execute tries, I think we executed very well," said Brown. "The defense was impressive at times. I think every player tonight dominated the contest defensively."

Tongan-born Amanaki Lelei Mafi and Asaeli Ai Valu scored first-half tries along with Timothy Lafaele, as Japan went on to claim a 21-0 halftime lead they never gave up.

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Japan and the United States are the only sides with two wins at the Pacific Nations Cup, meaning their clash next weekend in Fiji will decide the winner of the six-team tournament.

The U.S. Eagles, led by former Kobe Kobelco Steelers coach Gary Gold, defeated Samoa 13-10 at ANZ Stadium in Fiji earlier Saturday, a week after beating Canada 47-19.

The game at Hanazono was considered especially important because the 'Ikale Tahi play a physical game similar to their Pacific island neighbors, 16th-ranked Samoa, whom Japan will face in their third pool A match on Oct. 5.

Japan stuck to their game plan of kicking the ball to control the tempo of the match, and the forwards impressed by getting past the heavily-built Tongans by utilizing short passes.

Japan captain Michael Leitch, who played for the entire 80 minutes in his return to the starting lineup following injury, said he gave the team an "eight out of 10."

"Winning two in a row gives us confidence. We were able to do everything we wanted to do with only a week to prepare. We also made use of the lessons from our last game," he said. "I've noticed that we can improve even in the absence of the leader, the head coach."

"I really feel like the Japanese national team is improving. I think our opponents have noticed how we are changing," Leitch said.

With the temperature around 30 C at kickoff, the players and a sell-out crowd of 20,940 also had to battle the heat at the venue, which will host four World Cup matches.

The opening minutes saw Tonga dominate. But they could not make the most of a fourth-minute yellow card to Kotaro Matsushima. And Japan picked up the momentum with Mafi and Valu touching following driving mauls.

Scrumhalf Yutaka Nagare set up the final try of the first half with a well-placed kick, with Lafaele taking a good pass from Yu Tamura to go in under the posts.

While Japan slowed down and committed more errors in the second stanza, Tonga picked up the pace on Leva Fifita's 57th-minute try.

But Matsushima made up for his time in the sin bin by touching down for Japan's fourth try, before Kenki Fukuoka dotted down for the fifth, with Tamura adding his fifth conversion to go with two penalties.

Tonga head coach Toutai Kefu said, "(I'm) very disappointed. The lineout was poor, I thought we didn't get any good launch into the first phase, and we made far too many errors with our kicking."

Hanazono is considered the spiritual home of Japanese rugby as it stages the annual national high school championship and Tonga will play two of their four pool matches at the Higashiosaka venue.

Following next week's game in Fiji, Japan will play South Africa on Sept. 6 before the World Cup opens on Sept. 20.